Year of Hell
You may also be looking for the VOY Season 4 episodes "Year of Hell, Part I" and "Year of Hell, Part II." The Year of Hell was the name that Captain Kathryn Janeway gave to a series of conficts that the USS Voyager had with the Krenim during 2374. This occurred in two alternate timelines, one in which Kes was a member of Voyager's crew (VOY: "Before and After") and one in which Seven of Nine was a member of the crew (VOY: "Year of Hell"). In both cases, Voyager came under attack by a species called the Krenim, who used temporal-based weapons to attack, thus allowing their missiles to pass through Voyager's shields due to their being in a state of temporal flux. However, here the similarities end; in Kes's timeline in "Before and After", the Year of Hell led to the deaths of several officers, such as Captain Kathryn Janeway, Lieutenant Joe Carey, and Lieutenant Commander B'Elanna Torres, the Doctor's program was shut down for several months, and several crewmen were contaminated by chroniton radiation, although all were treated. In the aftermath of the disaster, Chakotay assumed command of Voyager, Neelix became a security officer, and the Doctor was restored with a full head of hair, as well as choosing the name 'Doctor Van Gogh', although he briefly thought about calling himself Mozart. As well as these, Kes married Tom Paris and they had a daughter, Linnis Paris, who married Harry Kim and had a son called Andrew Kim. This timeline eventually ended when Kes' past chroniton contamination was triggered by the Doctor's attempts to save her life with a bio-temporal chamber, resulting in her travelling backwards in time so far that she erased this history. In the timeline with Seven of Nine present, taking place during "Year of Hell, Part I" and "Year of Hell, Part II", under the command of Annorax, the Krenim had developed the Krenim temporal weapon ship, which possessed a weapon that could change history. They had used it to rewrite time in their region to regain their lost empire, but Annorax was fixated with restoring the colony that his wife had been on when he accidentally changed history and erased that colony from existence; he was even prepared to risk a Krenim Empire that had been 98% restored, so long as his wife's lost colony remained in that 2%. This had driven Annorax to the brink of insanity, so much so that he actually believed time itself had a grudge against him, and he refused to quit until the Krenim Empire was back to its full glory. As a result of being trapped in Krenim space, Voyager was heavily damaged by the Krenim's temporal-based weapons, until the crew were able to construct a temporal shield that deflected the firepower and allowed them to fight back. This also made them immune to Annorax's changes in history, although he was able to abduct Chakotay and Tom Paris before Voyager was forced to flee. Due to the damage sustained in constant battle with the Krenim, most of the crew were forced to evacuate Voyager due to the extensive damage, leaving only the remaining seven members of the senior staff to affect basic repairs. Having reconstructed Voyager to an extent that allowed it to work, Although they were forced to hide in a nebula for several weeks) the remaining crew formed an attack force consisting of Nihydron and Mawasi ships, in a desperate bid to stop the Krenim. Most of the crew split up to help prepare the small fleet for the assault, with Janeway remaining on Voyager to coordinate the attack, feeling that she 'owed' the ship to stay with it in its last great battle. In the final battle with the temporal weapon ship, its temporal core, which protected it from weapons fire and changes in the timeline, was shut down by a traitor and Chakotay and Paris were rescued. However, with Voyager's weapon systems down, and none of the other ships in any condition to do something either, Janeway was forced to set a suicide run at the weapon ship after ordering the fleet to take its temporal shields offline. As Voyager hurtled towards destruction, Janeway explained that the destruction of the weapon ship would most likely erase these events from history, adding "And this is one year I'd like to forget". As Voyager exploded against the weapon ship, Krenim warship exploded, and the ship's existence was subsequently erased, meaning that history was never altered to begin with. In this unaltered timeline, on a Krenim colony, Annorax is shown choosing to spend time with his wife instead of finishing his calculations for the construction of the ship. Voyager was thus able to pass safely through Krenim space, with no memory of these events having taken place, the Krenim simply advising them to keep their distance due to the territorial disputes and wishing them a good journey. Year of Hell, The